Recessed tab for higher energy density and thinner batteries

ABSTRACT

Various embodiments are described herein for an electrode assembly for a battery and a method of making the electrode assembly. The electrode assembly comprises an active material layer having a recess formed therein at an outer surface of the active material layer, the recess extending from a side facet of the active material layer toward an interior portion of the active material layer; a current collector layer supported on and in electrical contact with the outer surface of the active material layer; and a tab element supported partially within the recess and in electrical contact with at least one of the active material layer and the current collector layer, the tab element being adapted to provide an electrical connection for the electrode assembly.

FIELD

The embodiments described herein relate generally to energy storageelements and, more particularly, to battery structures.

BACKGROUND

Mobile devices are extensively used in everyday life. These mobiledevices are powered by batteries that are in most cases rechargeable butin other cases can be disposable. It is important in both of these casesthat these batteries have a high capacity so that they last a long timebefore having to be recharged or replaced as the case may be. However,mobile devices, such as handheld devices, have limited space forbatteries.

Therefore, it is important for batteries to be designed in aspace-efficient manner to provide a suitable amount of charge.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the various embodiments described herein,and to show more clearly how these various embodiments may be carriedinto effect, reference will be made, by way of example, to theaccompanying drawings which show at least one example embodiment, and inwhich:

FIG. 1 is an example embodiment of a method to manufacture an electrodeassembly for a battery;

FIG. 2A is a side view of an example embodiment of an electrode assemblyfor a stacked-cell battery;

FIG. 2B is a side view of another example embodiment of an electrodeassembly for a stacked-cell battery;

FIG. 3A is a side view of a portion of another example embodiment of anelectrode assembly for a stacked-cell battery;

FIG. 3B is a side view of a portion of another example embodiment of anelectrode assembly for a stacked-cell battery;

FIG. 3C is a side view of a portion of another example embodiment of anelectrode assembly for a stacked-cell battery;

FIG. 3D is a side view of a portion of another example embodiment of anelectrode assembly for a stacked-cell battery;

FIGS. 4A-4C are isometric, top and side views of another exampleembodiment of an electrode assembly for a stacked-cell battery shownwithout the tab elements for purposes of illustration;

FIGS. 5A-5C are isometric, top and side views of another exampleembodiment of an electrode assembly for a stacked-cell battery;

FIG. 6A is an isometric view of an example embodiment of a tab elementfor use with an electrode assembly;

FIG. 6B is an isometric view of another example embodiment of a tabelement for use with an electrode assembly;

FIG. 7 is an isometric view of an example embodiment of a stacked-cellbattery using the electrode assemblies described herein;

FIG. 8 is an isometric view of a portion of an example embodiment of anelectrode stack assembly having two electrode assemblies and variousexample configurations of tab elements for use in a stacked-cellbattery; and

FIGS. 9A-9E show various example embodiments of battery packconfigurations that are possible with the folded tab elements describedherein.

DESCRIPTION OF EMBODIMENTS

Various apparatuses or processes will be described below to provideexample embodiments of each claimed invention. No embodiment describedbelow limits any claimed invention and any claimed invention may coverprocesses or apparatuses that differ from those described below. Theclaimed inventions are not limited to apparatuses or processes havingall of the features of any one apparatus or process described below orto features common to multiple or all of the apparatuses or processesdescribed below. It is possible that an apparatus or process describedbelow is not an embodiment of any claimed invention. Any inventiondisclosed in an apparatus or process described below that is not claimedin this document may be the subject matter of another protectiveinstrument, for example, a continuing patent application, and theapplicants, inventors or owners do not intend to abandon, disclaim ordedicate to the public any such invention by its disclosure in thisdocument.

Furthermore, it will be appreciated that for simplicity and clarity ofillustration, where considered appropriate, reference numerals may berepeated among the figures to indicate corresponding or analogouselements. In addition, numerous specific details are set forth in orderto provide a thorough understanding of the embodiments described herein.However, it will be understood by those of ordinary skill in the artthat the embodiments described herein may be practiced without thesespecific details. In other instances, well-known methods, procedures andcomponents have not been described in detail so as not to obscure theembodiments described herein. Also, the description is not to beconsidered as limiting the scope of the embodiments described herein.

The embodiments described herein generally relate to energy storageelements for mobile devices and, more particularly, to various designsfor electrode assemblies for stacked-cell batteries that allow for atleast one of higher energy density, more compact stacks, and moreflexibility when connecting together various cells in a battery or whenconnecting together various stacked-cell batteries.

In battery configurations, the electrode assembly consists of an activematerial layer supported by a current collector layer. A tab element isconnected to the electrode assembly to make an electrical connectionwith the active material layer. The tab element is conventionally formed“in-line” with the current collector layer such that the height orthickness of the tab element and the current collector layer areapproximately equal. The tab element and the current collector layer arealso fixed to a common surface of the active material layer. Thiselectrode assembly forms the cathode or anode for a battery cell.

The minimum thickness of the current collector layer is limited due tothree issues with conventional battery manufacturing processes. Theselimitations are important since a thicker current collector layer willreduce the percentage of the active material layer to the overall areaof the electrode assembly (given size constraints on a battery) whichwill in turn reduce the energy density of the battery. However, theinventors have realized various designs with a thinner current collectorlayer that would result in more active material in the battery per unitvolume and, therefore, higher battery capacity per unit volume.

The first constraint on the thickness of the current collector layer isdue to the need for mechanical stability during manufacturing. Theactive material used for the anode and cathode layers in currentstacked-cell battery topologies is typically very soft and unstable. Forexample, for a typical portable electronic battery, the anode can bemade from graphite and the cathode can be made from lithium cobaltdioxide. There are also a number of other commercially viablepossibilities as is known by those skilled in the art. The teachingsdescribed herein can be used with these various different combinationsof materials. Accordingly, due to these soft and unstable materials, inorder to create the layers of an electrode assembly, conventionalmanufacturing processes first form the current collector layer, thendeposit the active material onto the current collector layer as a liquidor aqueous solution known as a slurry, and then cure the active materiallayer. After curing, the active material layer and its adherence to thecurrent collector may be still fairly fragile. Therefore, the currentcollector layer acts as a substrate for the active material layer duringmanufacturing to provide stability and mechanical strength to the activematerial layer. If the active material layer and/or the currentcollector layer were to break when the electrode assembly is beingmanufactured, the production line process would need to be shut down. Toprevent this from happening, the current collector layer isconventionally formed with a minimum thickness to provide the requiredmechanical strength and stability. This minimum thickness is also set,in part, by the throughput of the manufacturing equipment in order toavoid breakages in the electrode assembly while producing electrodeassemblies at a certain speed. A higher throughput speed then requiresgreater mechanical strength for the electrode assembly which in turnrequires a thicker current collector layer.

A second constraint on the thickness of the current collector layer isthe effect of the current collector layer on the Equivalent SeriesResistance (ESR) of the battery. Since the current collector layerconducts current to/from the external terminals of a battery cell, theeffective electrical resistance of the current collector layer isinversely proportional to the cross sectional area of the current flow,which in this case is the cross-sectional area of the current collectorlayer. In general, current collector layers with a larger thickness willhave a larger cross-sectional area which means a lower ESR for thebattery.

A third constraint on the thickness of the current collector layer isthe solderability of the tab element. In conventional batterytopologies, the tab element is generally ultrasonically welded orotherwise attached (using techniques known by those skilled in the art)onto the current collector layer. Since the tab element provides theonly electrical connection to the external terminals of the battery, ifthe tab element breaks, then the battery is ruined. The tab element istherefore conventionally designed to be thick enough to last for thelife of the battery. In some cases the tab element can be as thick asthe current collector layer to provide a better “matching”. Furthermore,the soldering, welding or attaching process may also, in some cases,punch through the current collector layer, which would potentially alsoruin the battery by shorting the electrodes. Both of theseconsiderations results in a minimum thickness for the current collectorlayer.

In conventional battery manufacturing processes, the most severe of theabove constraints dictates the minimum possible thickness for thecurrent collector layer. That is, the largest of these three respectiveminimum values provides the ultimate constraint on the thickness of thecurrent collector layer.

However, the inventors have discovered that the challenges with thethickness of the current collector layer due to conventional batterymanufacturing techniques can be overcome if the active material layercan be stabilized independently of the current collector layer.Referring to FIG. 1, shown therein is an example embodiment of a method100 to manufacture an electrode assembly for a battery. The method 100starts at step 102 where the active material for a battery electrodeassembly is deposited on a temporary backing substrate to form an activematerial layer. The active material layer comprises an electrolytepolymer. In at least some cases, the electrolyte polymer is mechanicallyself-stabilizing at ambient temperatures. In step 104, the activematerial layer is mechanically stabilized. The temporary backingsubstrate, which can be disposable or reusable, could be Mylar, the samematerial as the active material layer (Al or Cu), or any other materialthat meets the mechanical and temperature requirements (theserequirements are known by those skilled in the art). The real andreusable current collectors can be “pasted” together at their interfacesuch that they are easily separated from each other when needed duringstep 108. It should be noted that this mechanical stabilization isindependent of using the current collector layer as a backing substrate.

At step 106, once the active material layer is mechanically stable, arecess is formed on an outer surface of the active material layer;however this can also be done during step 104. For example, thetemporary backing substrate can be notched or shaped in such a way toprovide a negative mold with which to form a recess in the activematerial layer to receive the tab element. For example, the activematerial layer can be subjected to a rolling process to increase itsdensity and the recess can be formed by specifically compressing thisarea a little bit more than the rest of the active material layer. Thiscan be done with graphite material as the active material layer as it ismechanically robust to withstand some amounts of compression and can bedeformed under higher amounts of compression. When the active materiallayer is removed from the temporary backing substrate, a recess toreceive the tab element is already pre-formed into the active materiallayer. The recess can extend from any suitable facet of the activematerial layer toward an interior portion of the active material layerand at various positions along a given facet. For example, variousrecesses as described in FIGS. 2A-6 can be formed. In alternativeembodiments, the recess can be etched into the active material layerusing photolithography techniques, chemical etching or abrasive etching.Furthermore, in alternative embodiments, the recess can also be formedpre- or post the deposition or coating process. Other variations arealso possible as is known to those skilled in the art.

At step 108, the active material layer is removed from the backingsubstrate in such a way that the active material layer is not destroyed.Where there are two substrates, they can be separated using kinder,gentler processes such as being peeled without bending or stressing theactive material layer. Where the active material layer is completelyseparated, it will be much tougher. A binder could also be used andactivated to release the active material layer from the backingsubstrate. The separation process could be very gentle or the activematerial layers be made of materials that provide a mechanically robustcomposition. The material used for the binder is selected generally toachieve good adherence and a good ohmic contact for the tab element.However, the material for the binder can also be selected based on thepurpose of the battery as is known by those skilled in the art.

At step 110, the active material layer is isolated and a currentcollector layer is applied to the outer surface of the active materiallayer such that the recess is not filled in by the current collectorlayer. It should be noted that this step is the reverse of what istypically done in conventional battery manufacturing processes. Thecurrent collector layer can be printed on the active material layer orit can be formed from metal deposition or physically placed into therecess. In the case of metal deposition, in at least some cases, thecollector layer can be formed to be substantially continuous on theactive material layer. Barrier layers may also be used in certain casesto limit the amount of deposition as is known to those skilled in theart. In some embodiments, the current collector layer can also providethe material that is used for the tab element.

At step 112, a tab element is then secured at least partially within therecess area of the active material layer and attached to the currentcollector layer. Adhesion or barrier layers may be used for the tabelement as is commonly known to those skilled in the art. The tabelement can be mechanically welded or otherwise joined to the currentcollector layer. It should be noted that the tab element can generallybe adhered to its neighboring layers using any suitable chemical,electrical or mechanical means (e.g. compression) as is known to thoseskilled in the art. It should be noted that in some embodiments theorder of steps 110 and 112 can be reversed or combined.

With the manufacturing process 100, the three conventional constraintson the thickness of the current collector layer are significantly easedfor stacked-cell battery topologies since the current collector layer isnot stressed to mechanically stabilize the active material layer like itwould be during conventional manufacturing processes. Furthermore, in astacked-cell battery configuration, each battery cell, which includes ananode electrode assembly, an electrolyte and a cathode electrodeassembly, provides a separate electron conduction path which is thenconnected in parallel with the other battery cells. The resistance ofeach of these individual paths can therefore be higher (due to a thinnercurrent collector layer) than in conventional battery topologies sinceeach of these conduction paths are connected in parallel. In otherwords, rather than a single current collector layer with a thickness of14 microns (as would be used conventionally), two current collectorlayers each having a thickness of 7 microns and connected in parallelwould have the same overall ESR (even though each parallel conductionpath has twice the resistance compared to the 14 micron currentcollector layer).

With the manufacturing process 100, the thickness of the currentcollector layer is reduced such that the current collector layer isthick enough to be a continuous layer, is not islanded and still allowsfor the efficient collection of current. However, the current collectorlayer is thick enough to be connected to the tab element. In thisregard, the bond layer between the current collector layer and the tabelement can be Ohmic or thermal connections rather than Schottkydiode-type interfaces to avoid any voltage drops and non-linearity. Asan example, in cases where a conventional battery manufacturing processproduces an electrode assembly for a stacked-cell topology with an anodelayer having a thickness of 60 microns and a current collector layerhaving a thickness of 14 microns, the process 100 can be used to producean electrode assembly for a stacked-cell topology with an anode layer of65 microns and a current collector layer having a thickness of 9 micronsor even less, for example. Accordingly, the tab elements can be made“internal” or recessed into the active material layer so that the tabelements do not require extra thickness. In addition, various methodscan be used to improve the bond between the tab element and the currentcollector layer, such as low-energy, low-penetration microwavesoldering, with or without an absorption layer. Layer heating/coolingcould also be used to limit a weld's penetration capability. Aspreviously mentioned, various electrical, chemical or mechanicaltechniques can be used as is known to those skilled in the art. Forexample, conductive glue or paste may be used in some cases.

The battery manufacturing process 100 therefore provides a stacked-celltopology for a battery that makes use of recessed tab elements andcurrent collector layers with a reduced thickness in order to increasethe amount of active material (i.e. anode and cathode), or in otherwords the active/inactive material ratio, in the battery per unitvolume. While the thickness of the current collector layer is reduced,the thickness of the tab element is approximately the same as forconventional stacked-cell battery topologies, which results in the tabelement being recessed into the anode to preserve its thickness. Byreducing the thickness of the current collector layer and recessing thetab elements into the active material layer, battery capacity can besignificantly increased. For example, there can be an increased energydensity of about 10-15% for any given battery chemistry with theelectrode assembly designs described herein. In fact, this manufacturingtechnique can improve the energy density for stacked-cell batteries tobe on par or better than that of jelly-rolled batteries, especially forthinner battery form factors. Furthermore, thinner batteries can becreated using this manufacturing technique for a given energy rating.This electrode assembly topology can also be used to enableirregularly-shaped batteries, as is described in further detail below.It should be noted that in some embodiments the tab element may beformed by the current collector layer as previously described.

Various example embodiments of electrode assemblies for stacked-cellbattery configurations will now be discussed which incorporate a thinnercurrent collector layer. It should be noted that the manufacturingprocess 100, variations thereof or alternative manufacturing processescan be used to produce the following electrode assemblies.

Referring now to FIG. 2A, shown therein is a side view of an exampleembodiment of an electrode assembly 200 for a battery. The electrodeassembly 200 comprises an active material layer 202, a current collectorlayer 204 and a tab element 206. The electrode assembly 200 can be usedto provide a cathode or anode of a battery cell. At least a portion ofthe tab element 206 is located within the active material layer 202 sothat the current collector layer 204 can have a reduced thickness.

The active material layer 202 has a recess that is formed at its outersurface. The recess extends from a side facet of the active materiallayer 202 toward an interior portion of the active material layer 202 ina direction that is generally parallel to an end facet of the activematerial layer 202. The recess is also formed in the active materiallayer 202 such that it is spaced apart from an end facet of the activematerial layer 202. In this example, the recess has a rectangularprofile however other profiles can be used in other embodiments.

In this example and the other example embodiments described herein, thelocation of the recess can be varied along the side facet. Also, in thisexample and the other examples described herein, there can be otherembodiments in which the recess can be extend to a front or end facet ofthe electrode assembly. In addition, in this example and the otherexamples described herein, there can be other embodiments in which therecan be multiple recesses with each recess extending to a similar facetor to different facets of the electrode assembly in a linear ornon-linear pattern.

The active material layer 202 comprises an appropriate material suchthat the electrode assembly 200 acts as an anode or cathode as the casemay be. For instance, graphite can be used to provide an anode andlithium cobalt dioxide can be used to provide a cathode. There are alsoa number of other commercially viable possibilities as is known by thoseskilled in the art. In at least some cases, the active material layer202 is made from material that is mechanically self-stabilizing atambient temperatures such as, but not limited to, polymer or gelelectrolytes that are used in current Lithium polymer batteries.

The current collector layer 204 is supported on, and in electricalcontact with, the outer surface of the active material layer 202. Thecurrent collector layer 204 has a slot or recess to receive a portion ofthe tab element 206. Metal deposition can be used to form the currentcollector layer 204 on the active material layer 202. In at least somecases, metal deposition can be done such that the current collectorlayer 204 is substantially continuous on the active material layer 202,which may provide for a more reliable contact between the currentcollector layer 204 and the tab element 206. In this example, the outersurface of the tab element 206 can be flush with the current collectorlayer 204 or can be further recessed into the active material layer 202such that the current collector layer 204 is formed on top of it. Inalternative embodiments, there can be different vertical profiles forthe contact surfaces of the current collector layer 204 and the tabelement 206 which may provide certain advantages. For example, in somecases where there is higher current flow for high-power batteries, thesurfaces of the current collector layer 204 and the tab element 206which are in contact may be sloped or curved to reduce current densityin certain areas that would otherwise be at risk of “burning out” due tohigh current flow.

The tab element 206 is supported partially within the recess of theactive material layer 202 such that the tab element 206 is in electricalcontact with the current collector layer 204. Accordingly, the tabelement 206 and the portions of the current collector layer 204 and theactive material layer 202 that form the recess have complementarysurface profiles. In at least some cases, the tab element is bonded tothe current collector layer to provide an ohmic contact therebetween. Inthis example embodiment, the tab element 206 can be shaped to protrudeaway from the side facet of the active material layer 202 to provideelectrical connectivity with an external terminal of the battery or withanother electrical connection, such as possibly an intermediateelectrical connection with another battery cell. It can also be seen inthis example embodiment that the current collector layer 204 has athickness that is less than the thickness of the tab element 206.

It should be noted that the tab element 206 can be in differentlocations in alternative embodiments. The tab element 206 can beextended to the side, end or front facets of the electrode assembly 200and can be located at any position along these facets although thecorners may result in the highest current density and so it may bebetter to locate the tab element 206 at approximately the center of afacet of the electrode assembly 200 in some cases. Additionally,multiple positive and negative tab elements can be used in one or moreelectrode assemblies. The tab elements may be connected together as anoverlay, but this not an absolute requirement.

It should also be noted that two electrode assemblies are used to form abattery cell in which case there are two electrode assemblies 200 withan electrolyte material (not shown) in between them to allow electronsto flow between the two electrode assemblies. The active material layersare made of different materials so that one electrode assembly acts asan anode and the other electrode assembly acts as a cathode.

Referring now to FIG. 2B, shown therein is a side view of anotherexample embodiment of an electrode assembly 250 for a battery. Theelectrode assembly 250 comprises an active material layer 252, a currentcollector layer 204 and a tab element 256. In this case, the recess isformed such that the side walls 252 a and 252 b forming the recesswithin the active material layer 252 are sloped. In this case, the tabelement 256 has complimentary sloped portions to fit within the recessarea of the active material layer 252.

Referring now to FIG. 3A, shown therein is a side view of a portion ofanother example embodiment of an electrode assembly 300 comprising anactive material layer 302, a current collector layer 304 and a tabelement 306. The active material layer 302 has a recess 302 r that isshaped like a bisected octagon with upper ridges. The recess 302 r isdefined by a region of the active material layer 302 that comprises aflat floor portion 302 a, angled lower sidewalls 302 b and 302 c,straight sidewalls 302 d and 302 e and upper ridge portions 302 f and302 g. The walls 302 a-302 f do not necessarily have the same length butthere may be alternative embodiments in which they do have the samelength. The ridge portions 302 f and 302 g are generally between therecess 302 r and an end and front facet of the electrode assembly 300respectively. The ridge portions 302 f and 302 g end at a top surfacethat is generally planar with the outer surface of the active materiallayer 302. The top of the ridge portions 302 f and 302 g are generallyat a higher elevation than the floor portion 302 a of the recess 302 r.

The tab element 306 has a flattened octagonal shape that is defined bywalls 306 a-306 h. The walls 306 a-306 e have a complimentary shape tothe area of the active material layer defined by the walls 302 a-302 e.

In this case, the tab element 306 has upper inwardly angled walls 306 fand 306 g but in alternative embodiments these walls can be angledoutwards to match the walls 302 f and 302 g of the active material layer302 (which would also change the shape of the current collector layer304 in this region of the recess).

In this example, the current collector layer 304 has downwardlyextending triangular sections 304 a and 304 b. The triangular section304 a partially fills in the gap between the walls 302 f and 306 f andthe triangular section 304 b partially fills in the gap between thewalls 302 g and 306 g. The non-planar regions could be used astongue-and-groove guides in the stacking process and for overallmechanical stability of the multi-layer cell. However, there can bealternative embodiments with different shapes for the tab element 306and the current collector layer 304 as is shown in FIG. 3B.

Referring now to FIG. 3C, shown therein is a side view of anotherexample embodiment of an electrode assembly 350 comprising an activematerial layer 352, the current collector layer 304 and the tab element306. The active material layer 352 has a recess that is shaped like abisected hexagon. The recess is defined by a region of the activematerial layer 352 that comprises a flat floor portion 352 a and angledsidewalls 352 b and 352 c. The walls 352 a-352 c do not necessarily havethe same length but there may be alternative embodiments in which theydo have the same length. The walls 306 a-306 c of the tab element 306have a complimentary shape to the area of the active material layerdefined by walls 302 a-302 c although walls 306 b and 306 c are not thesame length as the walls 352 b and 352 c (however, in alternativeembodiments, they may have the same length in which there case therewould be no sidewalls 306 d-306 g). The triangular section 304 apartially fills in the gap between the walls 352 b, 306 d and 306 f andthe triangular section 304 b partially fills in the gap between thewalls 352 c, 306 e and 306 g. In an alternative embodiment, the portions304 a and 304 b can have a different shape so that there is no gapbetween these portions and the sidewalls 352 b and 352 c such as isshown in FIG. 3D. The configuration shown in FIGS. 3C-3D can occur in aprocess in which the tab element is attached first to the activematerial layer and the current collector layer is then formed by adeposition process which would fill the gap and cover all activematerial.

In FIGS. 3A-3D, at least a portion of the current collector layer 304 issupported between the active material layer 302/352 and the tab element306 within the recess. In addition, it can be seen that the tab element306 is generally supported between the active material layer 302/352 andthe current collector layer 304 within the recess. Furthermore, a topsurface of the tab element 306 is substantially planar with the outersurface of the active material layer 302/352; however, in otherembodiments this need not necessarily be the case.

It should also be noted that in FIGS. 3A-3B, the tab element 306 isshown attached to the current collector layer 304 whereas in FIGS. 3C-3Dthe tab element 306 is shown attached to the active material layer 352.This is because the process of forming these layers can be reversed.Also, in alternative embodiments, it should be noted that the sidewallsof the elements of the electrode assemblies 300, 300′, 350 and 350′ nearthe recess may be curved.

Referring now to FIGS. 4A-4C, shown therein are isometric, top and sideviews of another example embodiment of an electrode assembly 400 for astacked-cell battery shown without the tab elements for purposes ofillustration. The electrode assembly 400 comprises a first currentcollector 402, a first active material layer 404, an electricalinsulation layer (i.e. a separator layer) 406, a second active materiallayer 408, a second current collector 410 as well as first and secondrecesses 412 and 414 to receive tab elements (not shown). The electrodeassembly 400 has a side facet 416 and an end facet 418 that are bothvertical and orthogonal to one another. The active material layers 404and 408 and the current collector layers 402 and 410 are used to providethe same type of active portion for two different battery cells. Forexample, the current collector layer 402 and the active material layer404 can provide an anode for one battery cell while the currentcollector layer 410 and the active material layer 408 can provide ananode for another battery cell. Alternatively, the current collectorlayer 402 and the active material layer 404 can provide a cathode forone battery cell while the current collector layer 410 and the activematerial layer 408 can provide a cathode for another battery cell.

The recess 412 comprises a floor portion 412 a, an end wall 412 bgenerally opposing the side facet 416 and adjoining the floor portion412 a to an outer surface of the active material layer 404. The recess412 also comprises spaced apart side walls 412 c and 412 d extendingbetween an end wall 418 of the recess and the side facet 416 andadjoining the floor portion 412 a to the outer surface of the activematerial layer 404. The spaced apart side walls 412 c and 412 d aresloped inwardly toward the floor portion 412 a. The end wall 412 b isalso sloped inwardly toward the floor portion 412 a.

The recess 412 also comprises side walls 412 e and 412 f that extendvertically within the current collector layer 402 so that a tab elementwill be partially supported within the active material layer 404 and thecurrent collector layer 402. The end wall of the portion of the recesswithin the current collector layer 402 can be vertical (as shown in FIG.4A) or it can be sloped (as shown in FIG. 4B) in alternativeembodiments.

Conventional electrode assemblies for stacked-cell batteryconfigurations typically comprise pairs of anodes or cathodes separatedby an electrical insulator, similar to that shown in FIG. 4A except withno recesses in the active material layer and thicker current collectorlayers. These conventional electrode assemblies are then stacked one ontop of the other along with layers of electrolytes to form astacked-cell battery. Tab elements for the anodes and cathodes are thenformed on the same facet of the stacked-cell battery. The tab elementsare then drawn out laterally a relatively large distance away from thestacked electrode assemblies and joined together in order to beconnected to a Printed Circuit Board (PCB) or a Protection CircuitModule (PCM). The area between the stacked electrode assemblies and theedge of the PCB or PCM is often called the “Great Ears”, which wastessignificant volume within the battery because the tab elements can't bedensely formed together in the great ears region. This is partly done toavoid breaking the tab elements due to the mechanical stresses that arecreated from leading them away from the face of the electrode assembliesand connecting them with one another. This is also partly due to thefact that conventional practice is not to insulate the tab elementssince the tab elements are of the same polarity with the oppositepolarity tab elements being physically separated and distant.Consequently, the tab elements would have to run a certain length outfrom the face of the battery stack before being deformed in order toavoid shorting out the anodes and cathodes of a battery cell, whichwould likely be catastrophic for the stacked-cell battery. In addition,it is difficult to put a seal on the “great ears” region to insulate thetab elements assuming that the battery cells are stacked such that thosewith opposite polarity tab elements are stacked on top of each other forEMI reduction. Accordingly, it is prohibitively expensive to insulatethe “great ears” with conventional technology. Perhaps more importantly,it may not help to do so because proximity to opposite polarityconductors is not the primary limit to space reduction in the “greatears” configuration. While the great ears region may be on the order ofseveral millimeters, this issue is important as this region may take up2 to 10% of the volume in a typical stacked-cell battery. Givenconstraints in the sizes of batteries, especially for use in mobile andhand-held devices, this wasted space will reduce the volume of theactive portion of the battery, which will require disposable batteriesto be replaced more often or rechargeable batteries to be recharged moreoften. Furthermore, with this conventional configuration of tabelements, it is difficult to make a connection to a second stacked-cellbattery.

The inventors have found that a way to overcome the issue with the greatears region is to form the tab elements such that they are adjacent toone or more layers in the electrode assembly and/or a facet of theelectrode assembly. In other words, the tab elements can be positionedin at least one of the following ways: flush to an outer surface of anelectrode assembly, along an outer surface of an active material layerthat forms part of an anode or a cathode or along a surface of thecurrent collector layer that forms part of an anode or cathode. The tabelements may also be embedded into the electrolyte material in betweentwo electrode assemblies. This approach is more flexible thanconventional techniques as it provides more connection options since thetab elements can then be extended on whichever sides are most convenientfor the final product design rather than be limited by the batterydesign as is done in conventional techniques. In addition, this approachalso allows for the PCB or PCM to be positioned with improved proximityto the stacked-cell battery, thereby reducing the space that waspreviously occupied by the great ears. In fact, the volume of the regionwhere a stacked-cell battery is connected to a PCB or PCM can be reducedto less than 2% of the volume of the stacked-cell battery with thistechnique. This recovered space allows for a smaller battery pack (withthe same battery capacity) or increased battery capacity (e.g. 10-15%increased capacity) within the same battery pack volume. Furthermore,this approach allows a PCB or PCM to be connected to the stacked-cellbattery such that it is vertically-oriented instead ofhorizontally-oriented in a “patio” configuration which takes upadditional space.

Referring now to FIGS. 5A-5C, shown therein are isometric, top and sideviews of another example embodiment of an electrode assembly 500 for astacked-cell battery. The electrode assembly 500 comprises a firstcurrent collector layer 502, a first active material layer 504, aninsulator 506, a second active material layer 508, a second currentcollector layer 510 and first and second tab elements 512 and 514. Thecurrent collector layer 502 is adjacent to and in electrical contactwith an outer surface of the first active material layer 504. Thelayered elements of the electrode assembly 500 generally have a sidefacet 516 and an end facet 518.

The first and second tab elements 512 and 514 have insulated portionsthat are represented by cross-hatching and uninsulated portions 512 uand 514 u respectively. The tab element 512 has an end lead portion (notshown) that is in electrical contact with at least one of the firstactive material layer 504 and the first current collector layer 502. Thetab element 514 has an end lead portion (not shown) that is inelectrical contact with at least one of the second active material layer508 and the second current collector layer 510. The tab elements 512 and514 also have second lead portions (in this case side lead portions)that extend away from the end lead portions and are substantiallyadjacent to side facets 516 of the first and second active materiallayers 504 and 508. Portions of the insulated regions of the tabelements 512 and 514 provide an insulative layer that covers an innercontact area of the second lead portions of the tab elements 512 and 514to electrically insulate them from other regions of the electrodeassembly 500. The uninsulated portions 512 u and 514 u of the tabelements 512 and 514 provide an electrical connection to the electrodeassembly 500 such that the electrode assembly 500 can be electricallyconnected to an external terminal of the stacked-cell battery or toanother electrode assembly stack in a multi-stack battery.

The tab elements 512 and 514 can be made from different types ofmaterials such as, but not limited to, nickel and aluminum for example.In some cases, the tab elements can be made from polymer materials thatdissolve in the event of a short, thereby assuring safety as is known tothose skilled in the art. For example, bromine may be used.

The tab elements 512 and 514 can be pre-coated in an insulative polymermaterial and then bonded to the current collector layers 502 and 510respectively using a weld or other thermal/ohmic connection. The polymermaterial insulates the tab elements 512 and 514 from other battery celllayers and, in particular, the tab elements 512 and 514 are insulatedfrom the opposite electrode assembly from which the tab elements 512 and514 originate. Thus, if a given tab element is connected to a currentcollector layer of an anode, the polymer material insulates the giventab element from the cathode that completes the battery cell to preventelectrical short circuiting.

In order to insulate a given tab element, one option can be to coat theentire tab element with the polymer material and then cut away at eachend to provide uninsulated regions for electrically connecting to thetab element. A second option is to only cut away the polymer material atthe end of a given tab element that is being bonded to a PCB or PCM. Asuitable bond with a current collector layer may then be formed,effectively, by consuming the polymer material at the other end of thegiven tab element during the bonding process itself. For example, thepolymer material could melt away if the bonding is thermal or could, infact, be electrochemically consumed if the bond is made using some sortof catalytic material.

Since the tab elements 512 and 514 are electrically insulated, it is nowpossible to deform the tab elements 512 and 514 to achieve much denserformations than were possible with the conventional stacked-cellbatteries that had the “great ears” region. For example, as shown inFIGS. 5A-5C, it is now possible to deform the tab elements 512 and 514right up to the face of the stacked-cell battery and thereby occupy verylittle volume. By compressing the space that was previously occupied bythe “great ears”, it is now possible to form a tighter seal around thebattery cells. The result is a stronger seal, which makes thestacked-cell battery better able to withstand failure. Furthermore, thepolymer coating applied to the tab elements 512 and 514 also adds acertain amount of mechanical stability, which is useful as the tabelements are now being deformed to a greater extent than was doneconventionally. The polymer coating also allows for an increase in theradius of curvature wherever a given tab element or current collectorlayer is bent or contoured. Additional mechanical stability is due tothe fact that the tab elements 512 and 514 are now adjacent to largersurfaces and in fact immobilized against a facet or an inner layer ofthe stacked-cell battery, which makes the stacked-cell battery morerobust to withstand impact and shock or other mechanical stresses.

Referring now to FIG. 6A, shown therein is an isometric view of anexample embodiment of a tab element 600 for use with an electrodeassembly. The tab element 600 comprises an end lead portion 602, a sidelead portion 604, a bend portion 606 and a second end lead portion 608.The bend portion 606 adjoins the end lead portion 602 and the side leadportion 604. The bend portion 606 is formed substantially into a rightangle so that the end lead portion 602 can extend into an electrodeassembly to provide an electrical contact with at least one of an activematerial layer and a first current collector layer (shown in more detailin FIG. 8). A portion of the tab element 600 has an insulative layer asshown by the cross-hatched region. The insulative layer further coversthe first bend portion 606 of the tab element 600. The insulative layercomprises a polymer deposition. A periphery of the side lead portion 604is substantially encompassed by the polymer deposition along a length ofan inner contact area 604 i that will be substantially flush to an outerside facet of an electrode assembly. The tab element 600 can be used inembodiments in which the end lead portion 602 is received on the surfaceof an active material layer and juxtaposed to an adjacent currentcollector layer. Alternatively, the tab element 600 can be used inembodiments in which the active material layer has a recess to receiveat least a portion of the end lead 602.

Referring now to FIG. 6B, shown therein is an isometric view of anotherexample embodiment of a tab element 650 for use with an electrodeassembly. The tab element 650 comprises an end lead portion 652, a sidelead portion 654, a bend portion 656 and a second end lead portion 658.The tab element 650 is also covered with an insulative layer and issimilar to the tab element 600 except for the additional portion 652 awhich gives the end lead portion 652 a hexagonal cross-section. The tabelement 650 can be used in embodiments in which the end lead portion 652is received on the surface of an active material layer. Alternatively,the tab element 650 can be used in embodiments in which an activematerial layer has a recess to receive at least a portion of the endlead portion 652.

Referring now to FIG. 7, shown therein is an isometric view of anexample embodiment of a stacked-cell battery 700 using the electrodeassemblies described herein. The stacked-cell battery 700 comprises aplurality of electrode assemblies 702, 704, 706 and 708. Thestacked-cell battery further comprises a backing substrate 710 that isapplied to a side facet of the electrode assemblies 702, 704, 706 and708 so that any side lead portions of the tab elements are compactlyhoused between the electrode assemblies 702, 704, 706 and 708 and thebacking substrate 710.

Referring now to FIG. 8, shown therein is an isometric view of a portionof an example embodiment of an electrode stack assembly 800 having twoelectrode assemblies 800 a and 800 b and various example configurationsof tab elements for use in a stacked-cell battery. The electrodeassembly 800 a comprises a first current collector plate 802, a firstactive material layer 804, an insulative layer 806, a second activematerial layer 808 and a second current collector layer 810 allsupported in the electrode assembly 800 a. The second active materiallayer 808 and the second current collector layer 810 are bothelectrically insulated from the first active material layer 804 and thefirst current collector layer 802. The second electrode assembly 800 bcomprises a third current collector plate 812 and a third activematerial layer 814, an insulative layer 816, a fourth active materiallayer 818 and a fourth current collector layer 820 all supported in theelectrode assembly 800 b. The fourth active material layer 818 and thefourth current collector layer 820 are both electrically insulated fromthe third active material layer 814 and the third current collectorlayer 812. In this example, the first electrode assembly 800 a and thesecond electrode assembly 800 b are adjacently supported within theelectrode stack assembly 800.

The electrode stack assembly 800 further comprises a first tab element822 having a first end lead portion 824 in electrical contact with thefirst active material layer 804 and the first current collector layer802. In alternative embodiments, the first tab element 822 can have afirst electrical contact with at least one of the first active materiallayer 804 and the first current collector layer 802 and a secondelectrical connection with a portion of another electrode assembly orwith another element (this applies to similar connections describedbelow for other tab elements). The first tab element 822 also has anextended lead portion 826, which is a side lead portion that issubstantially flush to a side facet of the electrode assemblies 800 aand 800 b. The first tab element 822 has a bend portion 824 b that isformed substantially in a right angle to adjoin the first end leadportion 824 and the side lead portion 826.

The first tab element 826 further comprises another end lead portion 828in electrical contact with the first active material layer 804 and thefirst current collector layer 802. The first tab element 822 also has alateral lead portion 830 that extends away from the side lead portion826 into the electrode assembly 800 a and provides an electricalconnection 832 to the electrode assembly 800 a on a side opposite to theside on which the side lead portion 826 rests. The first tab element 822also has another lateral lead portion 834 that extends away from theside lead portion 826 into the electrode assembly 800 a and providesanother electrical connection 836 to the electrode assembly 800 a. Thelater lead portion 834 is adjacent to an outer surface of the currentcollector layer 802. The lateral lead portion 830 is between the outersurface of the active material layer 808 and the current collector layer810. The first tab element 822 also has a second bend portion 828 badjoining the side lead portion 826 to the lateral lead portion 834 andthe end lead portion 828 at an end of the side lead portion 826 that isopposite to the first bend portion 824 b.

A first insulative layer covers an inner contact area of the side leadportion 826 to electrically insulate the tab element 826 from each ofthe second and third active material layers 808 and 814. The first andsecond bend portions 824 b and 828 b also have insulated layers exceptfor where the end lead portions 824 and 828 make electrical contact withthe respective active material layer and/or current collector layer.

The electrode stack assembly 800 further comprises a second tab element838 having an end lead portion 840 in electrical contact with the secondactive material layer 808 and the second current collector layer 810.

The second tab element 838 also has an extended lead portion 842, whichis a side lead portion that is substantially flush to a side facet ofthe electrode assembly 800 a. The second tab element 838 has a bendportion 840 b that is formed substantially in a right angle to adjointhe end lead portion 840 and the side lead portion 842. The second tabelement 838 also has a lateral lead portion 844 that extends away fromthe side lead portion 842 and provides an electrical connection 846 tothe electrode assembly 800 a on a side opposite to the side on which theside lead portion 842 rests. The second tab element 838 also has asecond lateral lead portion 850 that extends away from the side leadportion 842 and provides an electrical connection 852 to the electrodeassembly 800 a. The lateral lead portion 850 extends into the electrodestack assembly 800 in between the first and second electrode assemblies800 a and 800 b and on a similar surface as the lateral lead portion830. In alternative embodiments, the lateral lead portion 850 can extendinto the electrode stack assembly 800 in between the first and secondelectrode assemblies 800 a and 800 b and on an opposite surface of thesame layer that the lateral lead portion 830 is on.

The electrode stack assembly 800 further comprises a third tab element854 having an end lead portion 856 in electrical contact with the thirdactive material layer 814 and the third current collector layer 812. Thethird tab element 854 also has an extended lead portion 858, which is aside lead portion that is substantially flush to a side facet of theelectrode assembly 800 b. The third tab element 854 has a bend portion856 b that is formed substantially in a right angle to adjoin the endlead portion 856 and the side lead portion 858. Although not shown here,the other end of the side lead portion 858 of the third tab element 854can provide an electrical connection to the second electrode assembly800 b or the third tab element 854 can have a lateral lead portion aslead portions 850 or 844 to provide an electrical connection to thesecond electrode assembly 800 b.

A second insulative layer covers an inner contact area of the side leadportion 842 to electrically insulate this portion of the tab element 838from the first active material layer 804. Likewise an insulative layercovers an inner contact area of the side lead portion 858 toelectrically insulate this portion of the tab element 854 from thefourth active material layer 818. The bend portions 840 b and 856 b alsohave insulated layers.

The side lead portions 842 and 858 can extend to other electrodeassemblies that are above and below, respectively, the electrodeassemblies 800 a and 800 b. In addition, since the tab elements areinsulated, at least a portion of the side lead portions 842 and 858 canoverlay the side lead portions of other tab elements.

It should be noted that the tab elements 822, 838 and 854 are similar tothe tab elements 512 and 514 and thus the techniques described toinsulate and connect the tab elements 512 and 514 to at least one of anactive material layer and a current collector layer also apply to thetab elements 822, 838 and 854.

As opposed to conventional battery stacks, which were constrained tolead away from a common battery stack face and form the “great ears”region, the tab elements described herein can follow any 3-dimensionalcontour within a battery pack. The folded tab elements can also be usedto make “local” connections, i.e., connections between differentstacked-cell batteries within a single battery pack. The ability to leadthe tab elements out from the stacked-cell battery following anyarbitrary trajectory is what makes it possible to synthesize batterypacks of arbitrary shape, piece by piece, from individual stacked-cellbatteries. Therefore it is now possible to form arbitrary 3-dimensionalshapes by combining multiple different stacked-cell batteries withoutwasting much space, whereas conventionally, because of past constraints,stacked-cell batteries were limited to rectangular geometries.

Referring now to FIGS. 9A-9E, shown therein are various exampleembodiments of battery pack configurations that are possible with thefolded tab elements described herein. These example embodiments showbattery packs with four different battery units (each unit can be asingle separate stacked-cell battery). However, it should be noted thatthis concept is not limited to four battery units and this concept canbe applied to more or less battery units and arranged in other geometricconfigurations.

FIG. 9A shows a battery pack 900 with stacked-cell batteries 902, 904,906 and 908 arranged in a linear configuration. FIG. 9B shows a batterypack 910 with stacked-cell batteries 912, 914, 916 and 918 arranged inan L-shape configuration. FIG. 9C shows a battery pack 920 withstacked-cell batteries 922, 924, 926 and 928 arranged in atriangle-shape configuration. FIG. 9D shows a battery pack 930 withstacked-cell batteries 932, 934, 936 and 938 arranged in a reverseL-shape configuration. FIG. 9E shows a battery pack 940 withstacked-cell batteries 942, 944, 946 and 948 arranged in a square-shapeconfiguration.

The battery pack configurations shown in FIGS. 9A-9E are possible byrunning the insulated tab elements along the faces of the differentbattery units, in 3 dimensions, to a common outlet and/or by running tabelements in between surfaces within each stacked-cell battery tofacilitate connection to one another. Being able to fabricateirregularly shaped batteries could be very useful to realize extrabattery capacity in mobile device configurations that impose form factorconstraints on the battery pack. For example, cell phone hardware maycreate a cavity within the phone casing that is not perfectly regular.However, with the tab elements and battery pack configurations describedherein, the battery pack can be designed to fit to the cavity, ratherthan designing the cell phone hardware to accommodate a regular shapedbattery pack.

It should be noted that the various embodiments and alternativesincluding the folded tab elements that were described with respect toFIGS. 5A-9 can be implemented alone or in conjunction with the variousembodiments that have recessed tab elements described in conjunctionwith FIGS. 1-4C.

In addition, the various embodiments described herein of stacked-cellbatteries that utilize folded tab elements can be used not only as anenabler for higher energy density batteries but also for batteries withmagnetically quieter designs. This is due to the ability to overlayinsulated tab elements on top of one another. If tab elements carryingcurrent in different directions are overlaid, the magnetic fieldsgenerated by opposite going currents in each of the tab elements may atleast partially cancel each other and reduce the overall magnetic fieldthat is generated. Therefore, if all the tab elements in thestacked-cell battery can be “paired” with a tab element that is carryinga similar magnitude current but in the opposite direction thentheoretically the tab elements should have a greatly reducedcontribution to the magnetic field that is generated by the stacked-cellbattery. This is important because the tab elements are often the mainsource of this magnetic field.

It should also be noted that the various embodiments described herein ofstacked-cell batteries that utilize folded tab elements can be used tocreate safer batteries depending on the choice of insulating polymersthat are used to insulate the tab elements. For example, the insulatingpolymers can be selected for “shutdown” characteristics in emergencysituations. Polymers could be used to activate a destructive propertythat dissolves at least a portion of the tab element and the currentcollector layer to remove any elements that have short-circuited inorder to shut down the problem. There are various ways to implement thisfeature as is known to those skilled in the art. For instance materialthat incorporates bromic acid can be used which is activated when thetemperate of the material rises above a certain critical temperature(which can occur due to a short circuit for example).

It should also be noted that if, for whatever reason, a pair ofelectrodes of opposite polarity should short out, a very large currentwill begin to flow in the stacked-cell battery, including within the tabelements and the current collector layers. However, if the currentcollector layers are thin enough relative to the magnitude of the shortcircuit current, the current collector layers may actually break due tothermal and mechanical stresses. In effect, the current collector layersmay double as fuses or circuit breakers. For example, if there is ashort between one of the anodes and its corresponding cathode, then oneof the corresponding current collector layers will burn and that cellwill be shorted but it will also be isolated from the remainder of thestacked-cell battery which provides for safer operation. This featurecan be enabled using recesses in the active material layer as describedwith respect to FIGS. 1 to 4C. To further enable this feature, thepolymer coating provides additional mechanical stability to the tabelements and current collector layers, which allows for a reduction inthickness to make the current collector layers even more suitable foroperation as fuses.

In addition, it should be noted that applying an insulating polymercoating on the tab elements makes it now possible to overlay the tabelements leading from electrodes of opposite polarity. For example, tabelements from cathodes may lead along a facet of the stacked-cellbattery at a first layer and tab elements from anodes may lead along thesame facet of the stacked-cell battery at a second layer at leastpartially on top of the first layer. By compacting and immobilizing thetab elements against the facet of the stacked-cell battery, moremechanical stability can be achieved, i.e., because there are now fewerparts leading away from or hanging off the facet of the stacked-cellbattery that would undergo mechanical deformation due to shock.

Furthermore, since the tab elements leading from opposite polarityelectrodes can be electrically insulated from each other with the designtechniques described herein, there is less risk of shorting due toinadvertent contact, which then makes it possible to increase thenumber/density of tab elements in the stacked-cell battery. Increasingthe number of tab elements will decrease the effective resistance of thebattery pack. The additional tab elements also provide some redundancywhen using more than one tab element for a given electrode assembly.This also reduces the maximum current density in the current collectorwhich reduces its thickness requirement as well as the ESR of theelectrode assembly. Accordingly, in case one or more of the tab elementsshould break during operation, the incremental change in effectiveseries resistance will be smaller than if there were fewer parallel tabelements.

In one aspect, according to at least one example embodiment describedherein, there is provided an electrode assembly for a battery. Theelectrode assembly comprises an active material layer having a recessformed therein at an outer surface of the active material layer, therecess extending from a side facet of the active material layer towardan interior portion of the active material layer; a current collectorlayer supported on and in electrical contact with the outer surface ofthe active material layer; and a tab element supported partially withinthe recess and in electrical contact with at least one of the activematerial layer and the current collector layer, the tab element beingadapted to provide an electrical connection for the electrode assembly.

In at least some cases, at least a portion of the current collectorlayer is supported between the active material layer and the tab elementwithin the recess.

In at least some cases, at least a portion of the tab element issupported between the active material layer and the current collectorlayer within the recess.

In at least some cases, the recess is formed in the active materiallayer spaced apart from an end facet of the active material layer.

In at least some cases, the recess extends away from the side facetgenerally parallel to the end facet.

In at least some cases, the active material layer comprises a ridgeportion between the recess and the end facet, the ridge portion having atop that is generally planar with the outer surface of the activematerial layer.

In at least some cases, the top of the ridge portion is at a generallyhigher elevation than a floor portion of the recess.

In at least some cases, the recess comprises a floor portion, an endwall generally opposing the side facet and adjoining the floor portionto the outer surface of the active material, and spaced apart side wallsextending between the end wall and the side facet and adjoining thefloor portion to the outer surface of the active material.

In at least some cases, the spaced apart side walls are sloped inwardlytoward the floor portion.

In at least some cases, the end wall is sloped inwardly toward the floorportion.

In at least some cases, the current collector layer comprises a metaldeposition onto the outer surface.

In at least some cases, the metal deposition is substantially continuousthroughout the current collector layer.

In at least some cases, the active material layer comprises anelectrolyte polymer.

In at least some cases, the electrolyte polymer is mechanicallyself-stabilizing at ambient temperatures.

In at least some cases, the tab element has a first thickness and thecurrent collector layer has a second thickness that is less than thefirst thickness.

In at least some cases, the tab element is bonded to the currentcollector layer to provide ohmic contact therebetween.

In at least some cases, an inner surface of the tab element and therecess have complementary surface profiles.

In at least some cases, a top surface of the tab element issubstantially planar with the outer surface of the active materiallayer.

In another aspect, according to at least one example embodimentdescribed herein, there is provided a method of producing an electrodeassembly for a battery. The method comprises providing an activematerial layer on a backing substrate; forming a recess in the activematerial layer at an outer surface of the active material layer, therecess extending from a side facet of the active material layer towardan interior portion of the active material layer; removing the activematerial layer from the backing substrate; applying a current collectorlayer to the outer surface of the active material layer; and securing atab element partially within the recess.

In at least some cases, the method further comprises stabilizing theactive material layer on the backing substrate prior to removing theactive material layer from the backing substrate.

In at least some cases, the current collector layer is applied to theouter surface of the active material layer prior to the tab elementbeing secured, and the tab element is secured to the current collectorlayer.

In at least some cases, the current collector layer is applied to theouter surface of the active material layer after the tab element issecured, and the current collector layer is applied over the tab elementwithin the recess.

In at least some cases, the current collector layer is applied to theouter surface of the active material layer as a metal deposition.

In at least some cases, the metal deposition is substantially continuousthroughout the current collector layer.

In at least some cases, the method further comprises bonding the tabelement to the current collector layer to provide ohmic contacttherebetween.

It should be understood that various modifications can be made to theembodiments described and illustrated herein, without departing from theembodiments, the general scope of which is defined in the appendedclaims.

1. An electrode assembly for a battery, the electrode assemblycomprising: an active material layer having a recess formed therein atan outer surface of the active material layer, the recess extending froma side facet of the active material layer toward an interior portion ofthe active material layer; a current collector layer supported on and inelectrical contact with the outer surface of the active material layer;and a tab element supported partially within the recess and inelectrical contact with at least one of the active material layer andthe current collector layer, the tab element being adapted to provide anelectrical connection for the electrode assembly.
 2. The electrodeassembly of claim 1, wherein at least a portion of the current collectorlayer is supported between the active material layer and the tab elementwithin the recess.
 3. The electrode assembly of claim 1, wherein atleast a portion of the tab element is supported between the activematerial layer and the current collector layer within the recess.
 4. Theelectrode assembly of claim 1, wherein the recess is formed in theactive material layer spaced apart from an end facet of the activematerial layer.
 5. The electrode assembly of claim 4, wherein the recessextends away from the side facet generally parallel to the end facet. 6.The electrode assembly of claim 4, wherein the active material layercomprises a ridge portion between the recess and the end facet, theridge portion having a top that is generally planar with the outersurface of the active material layer.
 7. The electrode assembly of claim6, wherein the top of the ridge portion is at a generally higherelevation than a floor portion of the recess.
 8. The electrode assemblyof claim 1, wherein the recess comprises a floor portion, an end wallgenerally opposing the side facet and adjoining the floor portion to theouter surface of the active material, and spaced apart side wallsextending between the end wall and the side facet and adjoining thefloor portion to the outer surface of the active material.
 9. Theelectrode assembly of claim 8, wherein the spaced apart side walls aresloped inwardly toward the floor portion.
 10. The electrode assembly ofclaim 8, wherein the end wall is sloped inwardly toward the floorportion.
 11. The electrode assembly of claim 1, wherein the currentcollector layer comprises a metal deposition onto the outer surface. 12.The electrode assembly of claim 11, wherein the metal deposition issubstantially continuous throughout the current collector layer.
 13. Theelectrode assembly of claim 1, wherein the active material layercomprises an electrolyte polymer.
 14. The electrode assembly of claim13, wherein the electrolyte polymer is mechanically self-stabilizing atambient temperatures.
 15. The electrode assembly of claim 1, wherein thetab element has a first thickness and the current collector layer has asecond thickness that is less than the first thickness.
 16. Theelectrode assembly of claim 1, wherein the tab element is bonded to thecurrent collector layer to provide ohmic contact therebetween.
 17. Theelectrode assembly of claim 1, wherein an inner surface of the tabelement and the recess have complementary surface profiles.
 18. Theelectrode assembly of claim 17, wherein a top surface of the tab elementis substantially planar with the outer surface of the active materiallayer.
 19. A method of producing an electrode assembly for a battery,wherein the method comprises: providing an active material layer on abacking substrate; forming a recess in the active material layer at anouter surface of the active material layer, the recess extending from aside facet of the active material layer toward an interior portion ofthe active material layer; removing the active material layer from thebacking substrate; applying a current collector layer to the outersurface of the active material layer; and securing a tab elementpartially within the recess.
 20. The method of claim 19, furthercomprising stabilizing the active material layer on the backingsubstrate prior to removing the active material layer from the backingsubstrate.
 21. The method of claim 19, wherein the current collectorlayer is applied to the outer surface of the active material layer priorto the tab element being secured, and the tab element is secured to thecurrent collector layer.
 22. The method of claim 19, wherein the currentcollector layer is applied to the outer surface of the active materiallayer after the tab element is secured, and the current collector layeris applied over the tab element within the recess.
 23. The method ofclaim 19, wherein the current collector layer is applied to the outersurface of the active material layer as a metal deposition.
 24. Themethod of claim 23, wherein the metal deposition is substantiallycontinuous throughout the current collector layer.
 25. The method ofclaim 19, further comprising bonding the tab element to the currentcollector layer to provide ohmic contact therebetween.